Field of the Invention
This invention relates to a ring-wing floating platform which has a dry wellhead and functions of drilling, production and storage. It can be used for oil and gas exploration, development and production.
Background of the Invention
Currently, the most common floating structures used for oil and gas field development and production in deep waters are four types: tension leg platform (TLP), spar, semi-submersible platform (SEMI) and floating production storage offloading unit or tanker (FPSO). The TLP and spar have the best hydrodynamic performance and drilling and production functions. They can be equipped with dry tree wellhead, yet they could not store oil. The hydrodynamic performance of SEMI is not as good as TLP and spar. It has functions for drilling and production. However, it could not be equipped with dry tree wellhead and doesn't have the function of storage typically. Ship-shaped FPSO has the worst hydrodynamic performance compared with the said three types. The greatest advantage of ship-shaped FPSO is it has functions of production and storage. However, it does not have drilling function and can't be equipped with dry tree wellhead. In addition, spar will have large heel under wind load considering its water plane area is small and draft is deep. SEVAN cylindrical FPSO, represented in U.S. Patent Document U.S. Pat. No. 6,945,736 B2, can be applied at sever sea states. Compared to traditional ship-shaped FPSO, its advantages are low cost and no requirement on single point mooring system. However, it has large heave motion and could not be equipped with dry tree wellhead.
Currently, a typical development plan for deep water oil field is: TLP or spar as wellhead platform (dry tree wellhead)+subsea pipeline+FPSO, or subsea wellhead+FPSO. Development of deep water gas field is slow and challenging, because the FPSO for production and storage of liquefied natural gas (LNG), called FLNG, is still in development stage, which can't produce and store LNG in harsh sea area. At present, the development usually adopts TLP or SPAR or subsea wellhead and relies on subsea pipelines to transport gases to shore directly, or to shallow water facilities first and then to shore. Gases would be liquefied in the shore base terminal and hauled away from seaports. In any way, plans using wellhead platforms or subsea wellheads, subsea pipelines and an FPSO or an onshore terminal for deep sea oil and gas field development would inevitably lead to complicated systems and facilities, high costs on engineering, construction, production, operation and field decommissioning.
Therefore, it is a major challenge of the offshore industry to replace the current development plan with a newly developed floating unit which has excellent hydrodynamic performance, storage capacities of crude oil, natural gas and LNG, and could be equipped with dry tree wellhead.